轻质合金无铆塑性连接方式及其关键技术的探讨

为了实现车身的轻量化,很多轻质材料如铝合金、镁合金等得到了广泛应用.无铆塑性连接在轻质材料的连接上具有巨大优势.无铆塑性连接利用板材的塑性变形产生机械锁而实现连接,可以应用于连接表面有镀层和不可焊接的板材.首先介绍了板材无铆连接方式及其机制,将其成形过程分为3个阶段.介绍了无铆连接的优点,并对无铆连接、锁铆连接和点焊等连接方式进行了对比.分析了轻质合金板材无铆连接的关键技术.无铆连接的关键技术包括模具几何形状参数、机械锁结构参数、被连接材料板材表面状况、塑性变形程度的大小及对失效模式的影响等.     

多层板高性能冲铆连接及铆钉形状合理性探讨

简述了现代工业对轻量化板材需求的迫切性,分析了多层轻量化板材连接的传统工艺存在的不足,阐述了多层板材塑性变形连接方式中有铆钉和无铆钉两种工艺的原理和工艺过程、优缺点.主要论述了有铆钉的冲铆塑性连接工艺的发展历程、应用领域、塑性连接机理和材料塑性流动行为.重点研究了铆钉形状为杯型、软与硬圆柱型、腰鼓型、尖头螺钉刺穿型等的...     

对称腰鼓式铆钉实现两层板材锁铆塑性连接特性研究

本文简述了现代工业对轻量化板材需求的迫切性,分析了多层轻量化板材连接的传统工艺存在的不足,简要分析了采用杯形刺入式的铆钉实现两层板材塑性变形连接的工艺过程及其存在的不足.提出了对称腰鼓形的铆钉实现轻量化板材的连接的新方式.明确指出平底腰鼓式对称铆钉连接的主要优势是通过铆钉和压边圈模具几何参数的设计,避免成形板材的下表面...     

板材无铆钉连接技术的进展

无铆钉连接技术是通过局部塑性变形而形成机械互锁的一种板料连接技术,无需额外的连接件,可以用于连接不同厚度和性能的薄板材料.由于无铆钉连接接头的强度受模具结构的影响,在一定程度上限制了该技术的应用,为了提高接头的连接强度、扩大其应用范围,国内外学者提出了一些新的改进工艺,如预制孔无铆钉连接、下板材预成形无铆钉连接、接头再...     

新世纪中国塑性加工行业的发展与展望

进入新世纪以来,在航空、航天、汽车和装备制造等行业的国家重大需求的牵引下,中国塑性加工行业获得快速发展,取得举世瞩目的成绩。根据2000年以来塑性加工行业获得国家技术发明奖和科技进步奖的情况,讨论了汽车覆盖件成形、高性能轻量化构件成形和多工位挤压等塑性加工关键技术的创新与发展,介绍了中国研制的超大型液压成形机、超大型环轧机、360 MN垂直挤压机和120 MN铝合金板材拉伸机等"世界第一"的超大型装备,展望了新世纪塑性加工技术发展趋势,包括:超大尺寸复杂构件塑性成形技术、轻质耐高温材料高性能复杂构件塑性成形技术、非理想材料塑性本构模型与高精度数值模拟、智能化塑性加工装备及生产线。     

交流伺服直驱无铆钉连接技术研究

无铆钉连接技术被广泛应用于汽车、航天以及家电行业金属板料的连接．主要加工薄板金属。虽然关于无铆钉连接的专利早在19世纪就已经出现了．但是上个世纪才被人们开始重视,尤其是随着汽车行业的快速发展以及人们对环境要求的不断提高．无铆钉连接技术也开始走进人们的视野,并广泛地应用到各个领域中。图1为无铆钉连接和有铆钉连接在汽车引擎盖上的分布情况。     

轻合金热态液力成形技术

铝合金和镁合金等轻合金在常温下变形能力差,但在加热到一定温度时塑性变形能力大幅提高.为了扩大此类轻合金在工业上,特别是在航空、航天以及汽车行业的应用,需要开发先进的温/热态成形技术.本文首先介绍了轻质合金的主要塑性成形方法,如超塑性成形,板材热冲压成形和气胀成形,然后重点讨论了铝合金及镁合金的热态液力成形技术的国内外研究现状,指出了开展此项研究的必要性和重要意义.     

塑性变形对钨铜板材显微结构及性能的影响

研究相对密度92%的熔渗烧结85W-Cu板坯冷轧变形行为.通过对板材中孔洞、钨颗粒变形行为的观测及XRD分析,得出85W-Cu板材的塑性变形机制.孔洞变形、弥合实现材料的致密化,钨颗粒经过纵向移动、横向移动、冷焊、变形过程,钨颗粒断裂贯穿整个塑性变形.材料的致密化和铜相、钨颗粒的变形产生的内应力导致材料显微硬度增加,最后材料失去塑性而失效.在800～930℃温区内对30%～40%变形量板材的退火能够改善材料的塑性.     

ABS热塑性高分子材料的电阻热铆焊工艺

采用铝铆钉连接热塑性塑料ABS,利用电阻点焊机快速加热使铆钉两端变形形成铆头,同时熔融塑料对被连接ABS板材起粘接作用,该方法兼具铆接、胶结及焊接的工艺特点。在试验焊接电流2.5 k A、3 k A、3.5 k A、3.7 k A、4 k A条件下,分析通电过程中由于焦耳效应,不仅铆钉发热变形,受热传递影响铆钉周围塑料熔化,在压力作用下向板间铺展,形成塑性熔合区;研究不同参数下接头拉伸载荷和断裂形式分析接头的连接机理,确定最佳工艺窗口;通过光电子能谱分析接头粘接界面母材成分及化学结构变化。     

30%碳纤维增强PA6复合材料的超声焊接-铆接复合连接工艺

该研究采用一种特殊设计的具有双凸缘结构的铆钉，制备了30%碳纤维增强PA6复合材料的超声波焊接-铆接复合连接接头，研究了焊-铆接头的宏观形貌、截面结构、失效形式、抗剪强度和剥离强度，并分析了焊-铆接头力学性能的改善机制。结果表明，超声波焊接-铆接复合连接的过程由库伦摩擦、铆钉铆入上板、铆钉铆入下板、焊合面材料熔化和凝固5个阶段组成。所制备双凸缘钉子的沟槽有效阻止了接头焊合面熔化材料的溢出，促进了铆钉与铆接板材间的机械互锁和铆钉周围焊核的形成，因此改善了焊-铆接头的抗剪强度、剥离强度和吸能性能。相对于抗剪强度，其对剥离强度的改善效果更显著。采用最佳焊铆参数下制备的焊-铆接头的抗剪强度和剥离强度较单一超声波焊接头分别提高了29.9%和39.2%。焊-铆接头的强度的改善缘于焊合面上铆钉周围形成的焊核及铆钉与铆接板材间的机械互锁的综合作用。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.